I have the APC H15 and the power cord is one of the most substantial I have seen (bigger than my power amp). APC quote 12 Amp rating because they are extremely conservative.

Frankly I can't see how a power cord can make a difference to any gear ( unless it has ACTIVE components inside that filter something ) Your APC S15 already has some inductors to clean up high frequency noise and to isolate each outlet device - this set of ACTIVE components in your APC is hundreds of times more important than any PASSIVE piece of wire (no matter how beautiful and "expensive" the esoteric power cord, it is essentially just a piece of wire like what you have around your house. (Caveat: some tightly "woven" power cord designs may actually have some mild inductive filtering properties for high frequencies, as an inductor is made from many loops of wire)

Furthermore, APC test their gear with high powered amplifiers so you can be assured that it won't limit current flow to the amp. Adding further filtering on top of the APC circuitry is ill advised IMHO (ultimaetly if you keep adding filters then you WILL restrict power to downstream devices).

BTW: I'm a tin-eared engineer so I am probably not to be trusted (being highly skeptical of any tweak that has no plausable physical or scientific explanation...)

A cable basically acts like an antenna for RFI and this can affect what you hear, as the interfearence ends up getting amplified. The most common approach is shielding and twisting of these cables to reduce RFI.

Every wondered why there is a little bulb like thingy on the cable connected to your computer's display unit. That is a ferrite block that is there to reduce intefearence otherwise even your cell phone will cause the display to distort. BTW adding a ferrite block to a power cable is not recommended unless you know exactly what to use and where as it can otherwsie make your system sound bad.

Whether or not a cable change will make a difference depends on how low the noise floor of your system is. Try any other cable as see if you hear a difference. If you do leave for a week and then change back. That is only way you can be certain that the new cable actually made a difference.

As far as the exotic cables go they are basically very expensive tone controls. In a system that has a very low noise floor any small change in material, construction of the power cable will result in a change in how the system sounds as it would for you by changing interconnects.

BTW there is a $60 power cable sold on Audiogon which apparently (according to the vendor) as as good as some of those exotic ones.